Growth Hormones in Food Animals: What’s the Risk?

Growth hormones are routinely given to cows and sheep being produced for their meat, and are injected into dairy cows. These hormones make their way to our dinner tables, and also contaminate the environment via manure and runoff from feedlots into local streams. Studies have shown that these factors can constitute risks to our health.

Why Are Hormones Given to Food Animals?

Since 1950 the US Food and Drug Administration (FDA) has allowed the use of steroid hormones in cows and sheep being produced for meat. These hormones promote growth and improve feed efficiency, key mineral absorption, and meat quality. Non-steroidal hormones such as rBGH (recombinant bovine growth hormone) are also injected into dairy cows to increase their milk production.

The hormones given to cattle and sheep are either provided via pellets injected into the animals or are mixed into the feed. If pellets are used, they are removed prior to slaughter to prevent unused hormones from finding their way into our meat.

Using the hormones translates to cost savings for the farmer and consumers. For beef, animals experience an 8-25% weight gain and a 10-15% gain in feed efficiency resulting in cost savings of $30 to $80 per cow. The meat that shows up at the grocery store should cost less for consumers, and the meat should be of better quality with an increased lean/fat ratio.

Poultry are not given hormones. So that chicken package you pay a bit more for because it says it is “hormone-free” is simply a marketing ploy. All chickens are produced hormone-free, although they may be given antibiotics, a variety of drugs, and genetically modified feed.

Poultry producers have no desire to use hormones in poultry as it is not cost effective and would require farmers to physically inject tens of thousands of birds several times a day. Poultry is fattened by feed which is typically genetically modified.

Other drugs and antibiotics are also routinely given to poultry, pigs, and cattle to promote better growth with less feed. Ractopamine is one example that is used in pigs. It is not a hormone, but is a drug that promotes growth. Many countries have banned its use.

Growth hormones are not used in “aquaculture” (fish farms) as they are prohibited by the FDA. Additionally hormones have not been shown to improve efficiency, growth or cost savings in farmed fish.

What you need to know about hormones given to cattle and sheep

Three natural steroid hormones and three synthetic hormones are used today in the US by beef cattle producers. The three synthetic hormones are trenbolone, melengestrol, and zeranol. The three steroid hormones are estradiol, testosterone and progesterone.

These hormones are also found naturally in people and all mammals. They are the primary reproductive hormones that play a role in sexual organ development, the onset of puberty, sexual maturation, and sexual behavior.

In sheep, three hormones are used primarily to control reproduction: progestogens, estrogens, and gonadotropins.

Researchers, including the FDA, agree that residues from these growth hormones can remain in meat after slaughter and also remain in the environment. Studies have shown that residual hormones such as trenbolone have found their way into local streams, and that these hormones have impacted normal reproductive functions and behavior in fish.

The FDA believes that the level of hormones found in grocery meats is well below any level of health concern. The administration points out that the steroid hormones given to cattle and sheep are also found naturally in these animals. Even without adding additional hormones, there are already estradiol, testosterone, and progesterone hormones in our grocery meat. The FDA says the natural and added levels of hormones in meat are acceptable.

While legal in the US, the use of certain steroid hormones in beef production is illegal in Europe, where it is banned based on concerns relating to potential impacts on people’s endocrine systems. European public health officials have said that even residual amounts of hormonally active compounds found in meat may have potentially adverse effects to public health.

They use what is called, “precautionary principle”. This means they want to protect people from being exposed to a risk before there is complete scientific proof that the risk exists. They feel any potential risk is just too great.

Many researchers disagree with the FDA’s stance and believe these incremental hormones act as damaging “endocrine disruptors” (EDs).

What’s an endocrine disruptor and why is it so dangerous?

The human endocrine system consists of the glands in our bodies that produce our hormones. Hormones regulate metabolism, tissue function, sexual function and reproduction, growth and development, sleep, and more.

It is well established that various toxic chemicals called endocrine disruptors (EDs) that people can be exposed to in the environment can affect their hormones. EDs can imitate natural hormones in the body and interfere with normal signaling. Of particular concern is that EDs mimic naturally occurring hormones such as estrogens, the female sex hormone. This can result in an increase or decrease in normal hormone levels or can alter the natural production of hormones.

So what does this mean? This hormone disruption can cause changes in metabolism, impair immunity, slow cognitive development, and result in fertility problems or even cancer.

One example of an endocrine disruptor many people have heard about is a drug called diethylstilbestrol (DES) that was given to some five million pregnant women to promote healthy pregnancies. It was later discovered that the DES had affected the normal development of the reproductive system in the fetuses, causing vaginal cancer. This is a great example of how impacts in endocrine function during early states of life can have major effects.

In particular, EDs affecting estrogens have been studied because elevated doses of estrogen hormones such as estradiol may cause premature sexual development in girls, including earlier maturation of breasts. Studies relating to the development of breast cancer have also been tied to exposure to estrogen-affecting EDs.

Many EDs have been labeled carcinogens as well. Science has shown that endocrine disruptors increase the risk for reproductive harm, premature sexual development, and diseases including cancer.

The challenge is whether or not hormones in our meat are truly endocrine disruptors, and what is an “acceptable level” if they are. Researchers are mixed on this point since it is difficult to pinpoint the precise effect on people given that they not only already have these hormones naturally in their bodies but also may be impacted by other endocrine disruptors in the environment or in foods other than meat.

An example of the complexity of the problem is a study of how meat prepared in fast food environments may contain EDs. Is the endocrine disruptor the hormone-fed beef? The GMO-feed the beef was fed? Is it other ingredients or high-heat cooking which may introduce endocrine disrupting chemicals? Is it the plastic chemical residue that comes from exposure to the cook’s protective gloves? Is it the packaging in which the food is delivered? There are just so many possible variables. This study found that children who got at least 35 percent of their calories from fast food had higher levels of endocrine disruptors in their urine. Yet with the toxic soup of possible EDs, to what extent is the beef the culprit?

Implications to children – premature sexual development?

Recent studies have shown that there has been a progressive decrease in the age of puberty onset in children. Most researchers agree that this is likely due to a combination of genetic, environmental, and endocrine factors.

Several EDs such as pesticides, phthalates, topical and natural estrogens, and phytoestrogens have been pointed to as possible agents affecting pubertal development in children. Some chemicals have actually been banned as they have been linked to affecting precocious puberty.

Chemical flame retardants have been linked to earlier menstruation. Pesticides and even hair products have been linked to earlier pubertal development. High levels of dioxin have been associated with increased risk for breast cancer.

Many different EDs have been found in urine of US girls when tested. In particular, bisphenol A (BPA – found in many plastics and the lining of canned foods) and phthalates have been routinely found in studies.

Phthalates have been found to trigger “death-inducing signaling” in boys’ testicular cells, making cells die abnormally early. Studies have also linked phthalates to lower sperm count, birth defects in the male reproductive system, thyroid irregularities and a variety of other disease states.

But what about hormones found in meat?

Scientists in the US still do not agree regarding the risk to children or adults relating to consumption of hormone treated meat. The FDA remains adamant that there is no risk. A small number of studies seem to disagree. The European restrictions follow the “precautionary principle” until more concrete data is available.

A variety of laboratory studies using human cells as well as animals do show effects. One animal study found that the hormone zeranol, used in cattle, created more rapid puberty onset.). Breast cells have been affected in studies using zeranol. Normal breast cells were affected, turning into cells exhibiting signs of early cancer development.

Another study showed that cattle hormones found in local streams interfered with reproductive processes and behaviors in fish.

Children who ate the most protein from animal sources were found, in a 2009 study, to enter puberty about seven months earlier than children who consumed the least amount of animal protein. But were their other factors involved?

Although conclusive evidence has not been found, many believe there is potential risk and that precautions should be taken.

* Purchase “sustainably-raised meat” from a local, sustainable farm. Just check with the farmer to ensure no hormones were used if the meat does not have the USDA organic label. Many smaller independent farmers do not use artificial hormones but may not be able to go through the certification required for the label due to cost.

* Don’t eat farm-raised fish. Wild-caught fish are preferred because farm-raised are often contaminated with endocrine disruptors and other toxins such as antibiotics. While farm-raised fish are not given hormones, they can be given feed that contains animals that may have been exposed to hormones. If you do eat farm-raised fish, try to find those labeled as not having been given antibiotics and not having been provided with feed that could include hormones. Many seafood suppliers and markets provide this type of information.